How to resolve the SOS malfunction in Audi A4?
2 Answers
Without disconnecting all the plugs of the OCU and the internal backup battery, reinstall the backup battery after 10 minutes and restore all the plugs on the OCU. Turn on the car's ignition and keep it on for 20 minutes, then disconnect the negative terminal of the vehicle's battery for about 3 minutes before reconnecting the negative terminal and starting the car. After starting the car, check if the SOS malfunction has been successfully resolved.
When I previously drove an Audi A4, the SOS warning light came on. I tried to fix it myself, starting with the simplest step: disconnecting the negative battery terminal for over ten minutes to reset it, which can clear temporary software glitches. If the light remains on, check the fuse box inside the car—commonly located on the driver's side—to see if the F18 fuse is blown. Replacing it costs just a few dollars. It could also be a faulty antenna module or control unit, in which case you’d need to visit an Audi dealership to scan for error codes with professional tools. Don’t forget that the car’s system sometimes requires a software update, which can be done via the Audi app or the connected infotainment system. The process can be complex, so prioritize safety—don’t delay repairs to avoid nighttime driving risks. Regularly monitoring battery health can help prevent similar issues.
